PURIFICATION AND LIGAND-RECEPTOR ANALYSIS OF INSULIN-RELATED PEPTIDES FROM PEDAL
GANGLION OF THE MOLLUSCA ANODONTA CYGNEA
Yu. I. Rusakov, A. P. Kolychev, V. N. Shipllov, V. M. Bondareva
The Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, St. Petersburg, Russia;
e-mail: bond_ver@mail.ru;
valshipilov@yandex.ru
Six insulin-related peptides (IRPs) from pedal ganglions of the molluscs Anodonta cygnea have been isolated
and purified by reverse-phase chromatography. Each peptide (designated as IRPS-IRP13) showed its own retention time on the HPLC
column. The testing of IRPs in radioreceptor systems specific for insulin and insulin growth factor-I (IGF-I) showed their ability to bind to
both types of receptors. The concentration of IRPs, producing a 50 % inhibition of porcine 125I-insulin binding with rat liver
plasma membrane receptors (IC50) for IRP10, was 1167 nM, IRP11 - 833 nM, IRP13 - 1333 nm. IRPS, IRP9, IRP12 in the
maximum concentration of 104 ng/ml displaced less than 50 % of labeled hormone. All of the six peptides were capable of competing
with human 125I-IGF-I for binding to receptors of a fraction of rat brain membranes. IRPS, IRP9 and IRP12 had close
means equal to 1167 nM, 1500 nM, 1167 nM, respectively. Another group including IRP10, IRP11 and IRP13 showed a much higher
activity (833, 83 and 500 nM, respectively). The results obtained from radioligand analysis revealed the predominance of IGF-I binding
properties in all peptides of pedal ganglions. At the same time, apparent proximity of IRP's physico-chemical characteristics to porcine
insulin, and also the revealed dose-depended binding to both insulin and IGF-I receptors suggest a bifunctionality of mollusc peptides.
The expression level of this bifunctionality may be associated with the molecular structure pecularities of individual isoforms
Key words: insulin, IGF-I, insulin-related peptides, molluscs
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